Using quantum chemical calculations, we have studied the oxidation of methane and small alkanes to the corresponding alcohols using nitrous oxide over well-defined active sites in metal-organic frameworks (MOFs).  These sites occur in the nodes of some MOFs as coordinatively unsaturated metal sites, for example in MOF-74, or as small metal-oxide clusters that can be synthesized using atomic-layer deposition (ALD) on OH-containing linkers in the MOF.  ALD creates the possibility of synthesizing a variety of cluster sizes and compositions, which can be evaluated computationally by understanding the mechanism and finding scaling relations.  Where possible, we make connections between these results and recent literature results for selective oxidation of methane over copper- and iron-containing zeolites.  We have also investigated nanoparticles (NP) encapsulated by metal–organic frameworks (MOFs) for regioselective catalysis. The regioselectivity in these materials arises from steric constraints imposed by the porous MOF structure, which limit the way molecules approach and interact with the metal surface. We have introduced a conceptually simple DFT approach to model reactions under such steric constraints and used this method to understand the potential of Pd NPs encapsulated in MOFs for the oxidation of n-butane to 1-butanol.  We also used a combination of DFT calculations and DRIFTS for adsorbed CO to characterize the nanoparticle-MOF interface.  These studies reveal that in Pt@ZIF-8, the ZIF linkers donate electron density to the Pt NPs, affecting their electronic structure.  DRIFTS measurements also show that the MOF linker can undergo an unexpected reaction with the Pt NPs during the encapsulation process.

Design and computational study of active sites in metal-organic frameworks for oxidation of alkanes

256th National Meeting (2018)

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